1. Field of the Invention
The present invention relates generally to an apparatus for making plates, and more particularly to an apparatus for making wedged plates.
2. Description of the Related Art
A conventional liquid crystal display (LCD) has a backlight module, which is typically classified into a direct-lighting backlight module and an edge-lighting backlight module. The edge-lighting backlight module has a light guide plate, which usually is a wedged plate and is made of Polymethyl methacrylate (PMMA), Polycarbonate (PC) Cyclic Olefins Polymer (COP) or Cyclic Olefins Copolymer (COC).
The light guide plate usually is made by injection molding, in which an injector is applied to inject melted plastic into a cavity of a mold. After the plastic has been solidified, the mold is opened to take the plate out. After that, the mold is closed to take next injection process. Injection molding is too slow for mass production because only one plate is molded in each process. While molding the large plate by injection molding, the plate might warp. In addition, the plate made by injection molding usually has unstable optical properties because there is residue stress in the plate.